Re: MMIO and gcc re-ordering issue

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To: Trent Piepho <tpiepho@...>

Cc: Linus Torvalds <torvalds@...>, Benjamin Herrenschmidt <benh@...>, David Miller <davem@...>, <linux-arch@...>, <linuxppc-dev@...>, <alan@...>, <linux-kernel@...>

Subject: Re: MMIO and gcc re-ordering issue

Date: Tuesday, May 27, 2008 - 2:33 pm

Trent Piepho wrote:
quoted text> Is there an issue with anything _besides_ coherent DMA?
> 
> Could one have a special version of the accessors for drivers that
> want to assume they are strictly ordered vs coherent DMA memory?
> That would be much easier to get right, without slowing _everything_
> down.

It's better to be safe by default and then optimize the fast paths than 
to be relaxed by default and hang the machine in some piece of code that 
runs once a month.  "Premature optimization is the root of all evil", 
and what not.

quoted text> One could even go as far as to allow a driver to "#define 
> WANT_STRICT_IO" and then it would get the strict versions.  Add that
> to any driver that uses DMA and then worry about vetting those
> drivers.

See above -- if you must have a #define, then it should be WANT_RELAXED_IO.

-Scott

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Messages in current thread:

[PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Tue May 20, 4:40 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Andreas Schwab, (Tue May 20, 6:00 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Tue May 20, 6:11 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Andreas Schwab, (Tue May 20, 6:47 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Tue May 20, 7:14 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Andreas Schwab, (Wed May 21, 4:03 am)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Wed May 21, 4:25 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Benjamin Herrenschmidt, (Tue May 20, 5:16 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Tue May 20, 6:00 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Benjamin Herrenschmidt, (Wed May 21, 10:00 am)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Wed May 21, 3:44 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Benjamin Herrenschmidt, (Wed May 21, 4:41 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Scott Wood, (Tue May 20, 5:38 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Alan Cox, (Tue May 20, 6:15 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Scott Wood, (Tue May 20, 6:35 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Tue May 20, 6:55 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Benjamin Herrenschmidt, (Wed May 21, 10:01 am)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, David Miller, (Tue May 20, 6:39 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Scott Wood, (Tue May 20, 6:43 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, David Miller, (Tue May 20, 6:53 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Benjamin Herrenschmidt, (Fri May 23, 12:24 am)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Thu May 22, 6:56 pm)

MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Mon May 26, 9:33 pm)

Re: MMIO and gcc re-ordering issue, Jonathan Corbet, (Tue May 27, 11:28 am)

Re: MMIO and gcc re-ordering issue, David Miller, (Mon May 26, 9:40 pm)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Mon May 26, 10:15 pm)

Re: MMIO and gcc re-ordering issue, David Miller, (Mon May 26, 10:28 pm)

Re: MMIO and gcc re-ordering issue, Alan Cox, (Tue May 27, 4:24 am)

Re: MMIO and gcc re-ordering issue, Arjan van de Ven, (Mon May 26, 11:42 pm)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue May 27, 3:08 am)

Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue May 27, 11:50 am)

Re: MMIO and gcc re-ordering issue, Pavel Machek, (Sat May 31, 4:04 am)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue May 27, 5:11 pm)

Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue May 27, 5:33 pm)

Re: MMIO and gcc re-ordering issue, Jes Sorensen, (Thu May 29, 10:47 am)

Re: MMIO and gcc re-ordering issue, Jeremy Higdon, (Sat May 31, 3:52 am)

Re: MMIO and gcc re-ordering issue, Jes Sorensen, (Mon Jun 2, 5:56 am)

Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 12:33 am)

Re: MMIO and gcc re-ordering issue, Jesse Barnes, (Tue Jun 3, 12:52 pm)

Re: MMIO and gcc re-ordering issue, Jes Sorensen, (Thu Jun 5, 4:40 am)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Thu Jun 5, 4:43 am)

Re: MMIO and gcc re-ordering issue, Matthew Wilcox, (Thu Jun 12, 11:07 am)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Thu Jun 12, 8:07 pm)

Re: MMIO and gcc re-ordering issue, Jeremy Higdon, (Tue Jun 3, 4:15 am)

Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 4:19 am)

Re: MMIO and gcc re-ordering issue, Jeremy Higdon, (Tue Jun 3, 4:45 am)

Re: MMIO and gcc re-ordering issue, Jeremy Higdon, (Mon Jun 2, 5:02 pm)

Re: MMIO and gcc re-ordering issue, Roland Dreier, (Thu May 29, 6:06 pm)

Re: MMIO and gcc re-ordering issue, Trent Piepho, (Thu May 29, 6:25 pm)

Re: MMIO and gcc re-ordering issue, Paul Mackerras, (Thu May 29, 11:56 pm)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Thu May 29, 5:40 pm)

Re: MMIO and gcc re-ordering issue, Jes Sorensen, (Fri May 30, 5:48 am)

Re: MMIO and gcc re-ordering issue, Pavel Machek, (Sat May 31, 4:14 am)

Re: MMIO and gcc re-ordering issue, Jes Sorensen, (Mon Jun 2, 5:48 am)

Re: MMIO and gcc re-ordering issue, Jesse Barnes, (Thu May 29, 5:53 pm)

Re: MMIO and gcc re-ordering issue, Jes Sorensen, (Fri May 30, 5:39 am)

Re: MMIO and gcc re-ordering issue, Trent Piepho, (Thu May 29, 5:48 pm)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Thu May 29, 6:05 pm)

Re: MMIO and gcc re-ordering issue, Trent Piepho, (Thu May 29, 9:53 pm)

Re: MMIO and gcc re-ordering issue, James Bottomley, (Thu May 29, 11:01 am)

Re: MMIO and gcc re-ordering issue, Jes Sorensen, (Fri May 30, 5:36 am)

Re: MMIO and gcc re-ordering issue, Jesse Barnes, (Fri May 30, 1:21 pm)

Re: MMIO and gcc re-ordering issue, Jeremy Higdon, (Sat May 31, 3:57 am)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue May 27, 6:13 pm)

Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue May 27, 6:39 pm)

Re: MMIO and gcc re-ordering issue, James Bottomley, (Tue May 27, 12:37 pm)

Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue May 27, 1:38 pm)

Re: MMIO and gcc re-ordering issue, James Bottomley, (Tue May 27, 1:53 pm)

Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue May 27, 2:07 pm)

Re: MMIO and gcc re-ordering issue, Chris Friesen, (Tue May 27, 5:23 pm)

Re: MMIO and gcc re-ordering issue, Paul Mackerras, (Tue May 27, 7:04 pm)

Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue May 27, 5:29 pm)

Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue May 27, 2:17 pm)

Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue May 27, 12:08 am)

Re: MMIO and gcc re-ordering issue, Arjan van de Ven, (Tue May 27, 12:20 am)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Mon May 26, 11:39 pm)

Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue May 27, 11:35 am)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue May 27, 5:10 pm)

Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue May 27, 5:30 pm)

Re: MMIO and gcc re-ordering issue, Alan Cox, (Tue May 27, 5:38 pm)

Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue May 27, 5:59 pm)

Re: MMIO and gcc re-ordering issue, Matthew Wilcox, (Tue May 27, 5:53 pm)

Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue May 27, 6:02 pm)

Re: MMIO and gcc re-ordering issue, Alan Cox, (Tue May 27, 5:46 pm)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue May 27, 5:38 pm)

Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue May 27, 5:55 pm)

Re: MMIO and gcc re-ordering issue, Russell King, (Mon Jun 2, 3:24 am)

Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 12:16 am)

Re: MMIO and gcc re-ordering issue, Trent Piepho, (Tue Jun 3, 3:43 pm)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue Jun 3, 6:26 pm)

Re: MMIO and gcc re-ordering issue, Matthew Wilcox, (Tue Jun 3, 5:33 pm)

Re: MMIO and gcc re-ordering issue, Trent Piepho, (Tue Jun 3, 5:44 pm)

Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 10:25 pm)

Re: MMIO and gcc re-ordering issue, Trent Piepho, (Wed Jun 4, 2:39 am)

Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue Jun 3, 10:47 am)

Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 10:19 pm)

Re: MMIO and gcc re-ordering issue, Trent Piepho, (Tue Jun 3, 2:47 pm)

Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue Jun 3, 3:07 pm)

Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 10, 2:56 am)

Re: MMIO and gcc re-ordering issue, Paul Mackerras, (Wed Jun 11, 1:20 am)

Re: MMIO and gcc re-ordering issue, Paul Mackerras, (Wed Jun 11, 12:18 am)

Re: MMIO and gcc re-ordering issue, Nick Piggin, (Wed Jun 11, 1:00 am)

Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Wed Jun 11, 10:46 am)

Re: MMIO and gcc re-ordering issue, Paul Mackerras, (Wed Jun 11, 1:13 am)

Re: MMIO and gcc re-ordering issue, Nick Piggin, (Wed Jun 11, 1:35 am)

Re: MMIO and gcc re-ordering issue, Paul Mackerras, (Thu Jun 12, 8:14 am)

Re: MMIO and gcc re-ordering issue, Nick Piggin, (Thu Jun 12, 9:08 am)

Re: MMIO and gcc re-ordering issue, Nick Piggin, (Wed Jun 11, 2:02 am)

Re: MMIO and gcc re-ordering issue, Jesse Barnes, (Tue Jun 10, 1:41 pm)

Re: MMIO and gcc re-ordering issue, James Bottomley, (Tue Jun 10, 2:10 pm)

Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue Jun 10, 3:05 pm)

Re: MMIO and gcc re-ordering issue, Jesse Barnes, (Tue Jun 10, 3:19 pm)

Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 10, 11:29 pm)

Re: MMIO and gcc re-ordering issue, Jesse Barnes, (Wed Jun 11, 12:07 pm)

Re: MMIO and gcc re-ordering issue, Nick Piggin, (Thu Jun 12, 7:27 am)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue Jun 10, 11:40 pm)

Re: MMIO and gcc re-ordering issue, Nick Piggin, (Wed Jun 11, 12:06 am)

Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 10:05 pm)

Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue Jun 3, 10:46 pm)

Re: MMIO and gcc re-ordering issue, Alan Cox, (Wed Jun 4, 7:47 am)

Re: MMIO and gcc re-ordering issue, Matthew Wilcox, (Tue Jun 3, 2:55 pm)

Re: MMIO and gcc re-ordering issue, Trent Piepho, (Tue Jun 3, 3:57 pm)

Re: MMIO and gcc re-ordering issue, Matthew Wilcox, (Tue Jun 3, 5:35 pm)

Re: MMIO and gcc re-ordering issue, Trent Piepho, (Tue Jun 3, 5:58 pm)

Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 10:00 pm)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue Jun 3, 12:32 am)

Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 2:11 am)

Re: MMIO and gcc re-ordering issue, Paul Mackerras, (Tue Jun 3, 2:53 am)

Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 3:18 am)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue Jun 3, 2:48 am)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue May 27, 6:19 pm)

Re: MMIO and gcc re-ordering issue, Arnd Bergmann, (Thu May 29, 3:10 am)

Re: MMIO and gcc re-ordering issue, Alan Cox, (Thu May 29, 6:46 am)

Re: MMIO and gcc re-ordering issue, Matthew Wilcox, (Tue May 27, 5:42 pm)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue May 27, 6:17 pm)

Re: MMIO and gcc re-ordering issue, Haavard Skinnemoen, (Wed May 28, 4:36 am)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Thu May 29, 9:13 pm)

Re: MMIO and gcc re-ordering issue, Haavard Skinnemoen, (Fri May 30, 2:07 am)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Fri May 30, 3:24 am)

Re: MMIO and gcc re-ordering issue, Haavard Skinnemoen, (Fri May 30, 4:27 am)

Re: MMIO and gcc re-ordering issue, Geert Uytterhoeven, (Fri May 30, 5:22 am)

Re: MMIO and gcc re-ordering issue, Haavard Skinnemoen, (Mon Jun 2, 4:11 am)

Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Wed Jun 4, 11:31 am)

Re: MMIO and gcc re-ordering issue, Scott Wood, (Mon Jun 2, 11:48 am)

Re: MMIO and gcc re-ordering issue, Haavard Skinnemoen, (Tue Jun 3, 3:46 am)

Re: MMIO and gcc re-ordering issue, Pantelis Antoniou, (Thu May 29, 7:05 am)

Re: MMIO and gcc re-ordering issue, Trent Piepho, (Tue May 27, 2:23 pm)

Re: MMIO and gcc re-ordering issue, Scott Wood, (Tue May 27, 2:33 pm)

Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue May 27, 12:47 pm)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue May 27, 5:12 pm)

Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue May 27, 1:31 pm)

Re: MMIO and gcc re-ordering issue, Ingo Molnar, (Mon Jun 2, 6:36 am)

Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Mon Jun 2, 5:53 pm)

MMIO and gcc re-ordering (Was: [PATCH] [POWERPC] Improve (in..., Benjamin Herrenschmidt, (Fri May 23, 8:36 am)

Re: MMIO and gcc re-ordering (Was: [PATCH] [POWERPC] Improve..., Benjamin Herrenschmidt, (Fri May 23, 8:50 am)

Re: MMIO and gcc re-ordering (Was: [PATCH] [POWERPC] Improve..., Scott Wood, (Fri May 23, 5:14 pm)

Re: MMIO and gcc re-ordering (Was: [PATCH] [POWERPC] Improve..., Benjamin Herrenschmidt, (Fri May 23, 6:47 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Benjamin Herrenschmidt, (Tue May 20, 6:02 pm)

Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Tue May 20, 6:21 pm)

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